netdev - Re: [PATCH net-next v2 6/9] xsk: add direct xmit in batch function

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Message-ID: <CAL+tcoBv3+uTx3A9=7kBnCzTgsDXUjtg7s9UJTpmxXneX3qigQ@mail.gmail.com>
Date: Tue, 26 Aug 2025 08:27:29 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Stanislav Fomichev <stfomichev@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, bjorn@...nel.org, magnus.karlsson@...el.com, 
	maciej.fijalkowski@...el.com, jonathan.lemon@...il.com, sdf@...ichev.me, 
	ast@...nel.org, daniel@...earbox.net, hawk@...nel.org, 
	john.fastabend@...il.com, horms@...nel.org, andrew+netdev@...n.ch, 
	bpf@...r.kernel.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v2 6/9] xsk: add direct xmit in batch function

On Tue, Aug 26, 2025 at 1:34 AM Stanislav Fomichev <stfomichev@...il.com> wrote:
>
> On 08/25, Jason Xing wrote:
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > Add batch xmit logic.
> >
> > Only grabbing the lock and disable bottom half once and sent all
> > the aggregated packets in one loop.
> >
> > Since previous patch puts descriptors in xs->skb_cache in a reversed
> > order, this patch sends each skb out from start to end when 'start' is
> > not smaller than 'end'.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> >  include/linux/netdevice.h |  3 +++
> >  net/core/dev.c            | 19 +++++++++++++++++++
> >  2 files changed, 22 insertions(+)
> >
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index 5e5de4b0a433..8e2688e3f2e4 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -3352,6 +3352,9 @@ u16 dev_pick_tx_zero(struct net_device *dev, struct sk_buff *skb,
> >
> >  int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev);
> >  int __dev_direct_xmit(struct sk_buff *skb, u16 queue_id);
> > +int xsk_direct_xmit_batch(struct sk_buff **skbs, struct net_device *dev,
> > +                       struct netdev_queue *txq, int *cur,
> > +                       int start, int end);
> >
> >  static inline int dev_queue_xmit(struct sk_buff *skb)
> >  {
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 68dc47d7e700..a5a6b9a199e9 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -4742,6 +4742,25 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
> >  }
> >  EXPORT_SYMBOL(__dev_queue_xmit);
> >
> > +int xsk_direct_xmit_batch(struct sk_buff **skbs, struct net_device *dev,
> > +                       struct netdev_queue *txq, int *cur,
> > +                       int start, int end)
> > +{
> > +     int ret = NETDEV_TX_BUSY;
> > +
> > +     local_bh_disable();
> > +     HARD_TX_LOCK(dev, txq, smp_processor_id());
> > +     for (*cur = start; *cur >= end; (*cur)--) {
>
> skbs support chaining (via list member), any reason not to use that for
> batching purposes?

Good point, let me dig into it :)

Thanks,
Jason